The present invention relates to a numerical control system for highly dynamic processes.
In particular, the present invention relates to a numerical control system for performing a path interpolation for the control of highly dynamic processes, such as for spark erosive metal machining and laser machining. A numerical control system of the type is known from the book "Rechnersteuerungen von Fertigungseinrichtungen", by R. Nann, ISW 4, Springer-Verlag, Berlin, Heidelberg, New York, 1972, pp 113-123. In the known control system, a coarse interpolator operates in a fixed time grid, a linear fine interpolator connected downstream of the coarse interpolator is operated in the same time grid. Data exchange between the coarse interpolator and the fine interpolator also takes place within this time grid at predetermined time intervals. When a path interpolation is required for slightly curved contours, the performance of the coarse interpolation and the fine interpolation in a common fixed time frame leads to an unnecessarily small node spacing, and an unnecessary data flood is produced. As a result, the coarse interpolator has to perform unnecessary calculations. Another problem resulting from the interpolation in the fixed time grid occurs when calculating the last nodes at the end of the path calculated by interpolation, if a specific end point of the path is to be reached. Conventionally the last path element has a length differing from that of the preceding path elements, so that the path end point can only be reached in the fixed time grid through a speed jump.
The book "Interpolation in numerischen Bahnsteuerungen" by D. Binder, ISW 24, Springer-Verlag, Berlin, 1979, pp 60-113 describes and compares various interpolation processes, which are also bound to a fixed time grid. Pages 113 and 114 of this book disclose a linear fine interpolator working according to the "Pulse-Rate-Multiply" process. However, such a fine interpolator does not permit rearward interpolation. Another disadvantage of this fine interpolator is that fine interpolation can only be performed over the entire range of the interpolator.